Electronic stimulator



July 12, 1955 D. MOSTOFSKY ET Ai.

ELECTRONIC STIMULATOR 3 Sheets-Sheet l Filed OCT.. 22, 1952 July 12,1955 D. MOSTOFSKY ET A1. 2,713,120

ELECTRONIC STIMULATOR Filed om. 22, 1952 s sheets-sheet 2 JWM EN .Www NW.m mw N- l1- i 4| Q3 H 11| Si @n m bvwl www X823 XN mi EN w QQ m -TLVwww THE/R HTToR/vsys July 12, 1955 D, MOSTOFSKY ET AL 2,713,120

ELECTRONIC STIMULATOR Filed Oct. 22, 1952 3 Sheets-Sheet 3 u LLI IS I-lUnited States Patent O ELECTRONIC STIMULATOR David Mostofsky, Brooklyn,and Alexander Sandow, New York, N. Y., assignors, by mesne assignments,to the United States of America as represented by the Secretary of theNavy Application October 22, 1952, Serial No. 316,292

10 Claims. (Cl. Z50- 27) This invention relates to electronicStimulators and is directed particularly to a high current output, dualpulse, electronic stimulator for physiologic purposes.

Physiologie Stimulators heretofore used were generally electronicdevices which produced variously shaped voltage pulses for applicationdirectly through wires to living structures such as nerve or muscle. Avoltage output was suitable in such cases, for the living tissueinvolved opposed the ow of current with a high impedance (of the orderof 1000 ohms or more), and the electric power required, therefore, wasinsigniiicantly small.

A new stimulation technique has recently been developed in which aphysiologic structure, a muscle, for example, is immersed in anelectrolytic bath containing two large so called massive silver-silverchloride electrodes symmetrically anking the muscle. An electricstimulating pulse must pass from electrode to electrode through theintervening electrolytic solution and on its way stimulate the musclesupported in the electrolyte. The actual impedance of such a massiveelectrode system is in the order of 9 ohms. To cover the varied needs ofthe physiologic experiments, currents ranging from a fraction of anampere to as high as 5 amperes are required to activate the contractileresponse of the muscle. It is manifest that under such conditions ofstimulation, high impedance output voltage generators heretoforeemployed in direct connection with the muscle have inappropriatecharacteristics.

Accordingly, it is one object of this invention to provide an electricstimulator that can produce high-current pulses across an uncommonly lowimpedance.

it is @other object to provide a stimulator of the character describedthat can produce a unit-cycle consisting of two rectangular pulses eachof which is independently variable, in duration from 30 to 25,00()microseconds, and in amplitude.

It is another object to provide a stimulator of the above nature whereinthe individual pulses comprising the unitcycle can be set, selectively,to be of either the same or opposite relative polarity.

t is another object to provide a stimulator of the character describedwherein the interval separating the individual pulses of the unit-cycleis independently variable in duration from zero to 25,000 microseconds.

It is a further object ofthe invention to provide such a stimulatorwherein the timing variables are smoothly and continuously adjustable.

It is a further object of the invention to provide such a stimulatorwherein the unit-cycle can be obtained on demand either once, orrepetitively at rates from one every ten seconds to 600 per second foran indefinite or limited time interval.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the following drawings wherein:

2,713,120 Patented July 12, 1955 Fig. 1 is a block diagram of theimproved stimulator illustrating pulse wave shapes from circuit tocircuit.

Fig. 2 is an electrical schematic diagram of the pulse generator andsynchronizer circuits of the improved stimulator.

Fig. 3 is an electrical schematic diagram of the power amplifier circuitof the improved stimulator; and

Fig. 4 illustrates the massive electrode arrangement for stimulation ofa muscle experimented upon in accordance with the invention.

The overall operation of the stimulator as illustrated in Fig. 1 willfirst be given. The rst pulse of a unit-cycle is initiated by a positivetrigger pulse 10 of about 30 volts supplied by a separate triggergenerator, (not shown). The trigger generator can be, for example, avariable frequency thyratron-controlled relaxation oscillator. Suchpulse generators are well-known in the art and therefore not furtherdescribed herein. The input pulse l() triggers the iirst phantastron 12,the time interval of which determines the time of the first pulse.

The output wave-form of the phantastron circuit 12 is trapezoidal, asindicated by the numeral 14. Therefore two shaping circuits 16 and 18follow, the first providing an output wave-shape as indicated by thenumeral 20, and the second the required substantially rectangularwave-shape 22. The second Shaper 18 also functions as a mixer when it isdesired that the two unit-pulses be of the same polarity, (ashereinbelow more fully described); the second pulse being introduced inits output circuit. The shaper-'nixer stage 18 is followed by a driverstage 24, which produces a large rectangular pulse 26 of about 230 voltsfor input to a power amplifier stage 2S.

The output of the first phantastron 12 is also fed through a cathodefollower 30, the output wave-form of which is indicated by the numeral32, to a differentiating circuit or peaker 34. The output wave-form ofthe peaker, indicated by the numeral 36, comprises a positive spikecorresponding to the trailing edge of the first phantastron pulse 14,and is used toV trigger a blocking oscillator circuit 38 to provide anarrow pulse 4i) of the order of l microsecond in duration. This pulse,in turn, is fed into an interval phantastron 42, which determines theinterval between the individual pulses of the unit-cycle.

The output 44 of the interval phantastron 42 is fed through a cathodefollower 46, the output 48 of which is fed into a second differentiatingcircuit peaker 50. The output 52 of the peaker 5l) comprises a sharppositive voltage pulse that is used to trigger a second blockingoscillator 54. A sharp trigger voltage 56 is obtained from the secondblocking oscillator. This marks the trailing edge of the outputwave-form 44 of the interval phantastron and initiates the action of athird phantastron 58, thereby determining the beginning of the secondoutput pulse of the unit-cycle. Therefore, the interval between thetrailing edge of the first pulse and the beginning of the second pulseis determined by the time of the interval phantastron 4 2. Y

The output 66 of the third or pulse 2 phantastron S8 is trapezoidal,like that` of the lirst or pulse l phantastron 12, and is followed by anamplier-shaper 62 to obtain a rectangular pulse 64, which is fedselectively through a single-pole double-throw switch 66 either to amixer-Shaper 63 or a Shaper 70, depending upon whether it is desired tohave the individual pulses of the unit-cycle of the same or oppositepolarity. Thus, if the switch 66 is thrown to the right, as shown in thedrawing, the pulse 64 from the amplifier-Shaper 62 is fed through theshaper 70, the output of which is a negative rectangular pulse 72, intoa driver stage 74,

0 the output 76 of which is a positive rectangular pulse 46, thencedirectly into the power amplier 28, whereby an output unit-cycle 78having individual pulses of opposite relative polarity is produced, ashereinbelow more fully described. If the switch 66 is thrown to theleft, as indicated by the dotted-line position, the pulse 64 is tedthrough the mixer-Shaper 68, the output of which Pulse generator andsynchrolzzer circuit description The basic timing and pulse-formingaction of the stimulator is performed by the identical phantastroncircuits comprising the pentodes 82, 84 and S6 for the pulse lphantastron, the interval phantastron, and the pulse 2 phantastron,respectively (see Fig. 2). Since the action of phantastron circuits hasbeen fully described in the literature (see, for example, the article:Design of Phantastron Time Delay Circuits, published in the April 1948issue of Electronics page 10G) it is deemed sufcient to say here thatthe output of such a circuit is a negative trapezoidal pulse, smoothlyvariable over a wide range and with a fall and rise time that is quiterapid. Individual diodes comprising the vacuum tube 88 are included inthey grid circuits of each of the phantastron circuits to permitoperation at rates up to 600 or more unit-cycles per second with therelatively wider pulses and intervals. These diodes peru mit a morerapid recovery of the grid voltage after the pulse.

The timing of the phantastron pulses is determined by the voltageapplied to the pentode plates, and, except for extremely narrow timeintervals, there is a linear relationship between this voltage and thepulse width. Thus, inthe pulse 1 phantastron circuit, the controlvoltage is applied to the plate of the pentode 82 through a diode 9i)which isolates the plate from `the `control voltage during thephantastron cycle when the plate voltage is lowered. The two 500) ohmpotentiometers 92, 94 in the phantastron circuit are adjustw ments thatdetermine the maximum and minimum voltage obtained from the 20,000 ohmpotentiometer 96, which is the phantastr'on pulse width control. rThe50i) ohm potentiometer 9d is a tine control. The condenser 100,connected from the cathode of the diode 9i? to ground, makes theadjustment of the `potentiometers smooth, and permits the location ofthe potentionieters to be remote from the phantastron circuit.

The output of the pulse 1 phantastron is taken from the cathode of thepentode d2.' This trapezoidal voltage pulse (see pulse 14 of Fig. l),goes to the grid of pulse.

20 of Fig.Y 1). This pulse is coupled to the next stage through a largetime constant network comprising the condenser 164i, the resistor 106and potentiometer E158. The diode 116 connecting the grid side of thecondenser 104 to ground is a clamper or D C. restorer which keepsV theD. C. level on the grid of the succeeding Stage fixed, despite widechanges in pulse rate, pulse width, and setting of the potentiometer 1%connected to the grid of the triode112 comprising the following stage.The potentiometer lt determines the ,amplitude of the output pulses. Thetriode 112 is biased to cut- O so hat only the positiveY part of thepulse is amplifled. The negative overshoot portion, therefore, is notobtained in the plate circuit of this tube. It will be noted that theplate of the triode 112 is connected to the plate of the triode 114, butsince these tubes are each biased to cut-ofi they do not load eachother. It can be seen, however, that a pulse introduced on the Agrid ofthe triode 114 will appear at the plate of the triOde 112.

From the plate of the triode 112, the rectangular i When pulses in theunit-cycle of opposite polarity are pulse, which is now negative (seepulse 22, Fig. 1) is applied to the grid of a vacuum tube 116, which isthe driver stage for the power amplifier, to be described hereinbelow.driver tube 116 supplies its own restorer action, since its cathode isdirectly connected to ground and the pulses are negative at the grid.

The pulse interval is the time from the trailing edge of the iirst pulseto the beginning of the second pulse. This interval is determined by theduration of the intervai phantastron circuit comprising the pentode 84.YThis phautastron is triggered by a spike that corresponds to thetrailing edge of the first phantastron output pulse (see pulse 49 ofFig. l). Y

The pulse on the cathode of the rst phantastron pentode 82 not only isconnected to the shaping circuits, as hereinabove described, but alsogoesto a trigger-forming circuit by way of a cathode follower circuitcomprising the triode 11S, which isolates the rst phantastron circuitfrom the circuits that follow. The action of the triode 12% followingthe cathode follower stage is to diterentiate the trapezoidal pulse.Thus, on the secondary of the pulse transformer 122 in the plate circuitofV phantastron. The tlow of current through the triode 121i` passesthrough a blocking oscillator transformer 132 whence, by transformeraction, this current is applied regeneratively to the grid of the triode1.23 to initiate the blocking oscillator action. The blocking oscillatortriode 123 is biased to cut-oir by the network comprising voltagedivider resistors 134 and 136 which supplies voltage v to the secondgrid of the interval phantastron pentode 84. The sharp positive pulse(see pulse 4@ of Fig. l), from the cathode of the blocking oscillatortriode i223 is directly coupled to the interval phantastron pentode S4,which it triggers. The time from the beginning to the end of theinterval phantastron pulse (see pulse 4e of Fig. l), determines the timeinterval between'the two output pulses of the stimulator.

The output of the interval phantastron'comprising the pentode 84 isVdiii"erentiated and a blocking oscillator pulse corresponding to thetrailing edge is obtained iu the same manner as described above. Thus,the circuits associated with the tubes 138, 149, 142, and 144 are thesame as those of tubes 11S, 120, 124 and 123, respectively. The outputvoltage spike of the blocking oscillator comprising the triode 144triggers the pulse 2 phantastron pentode 86, the output pulse of whichafter shaping, determines the second rectangular output pulse.

The output of the pulse 2 phantastron is shaped in the amplienshapercomprising the triode 146 and then is utilized in one of two ways,selectively. lf a unitcycle of two rectangular' output pulses of thesame polarity is reguired, the pulse from the triode 1.45 is switched,by means of the double-pole doublethrow switch 148, to the grid of thetriade 11d from which, by way of the plate register 155? common to thetriode 112, it is applied to the driver comprising the triode i316.

desired, the pulse from the triode 146 is switched to a Shaper circuitcomprising the triode 152, from the piate of which it goes to the gridof a second driver comprising the tube 154. The reason for thisswitching will be apparent in the following description of the poweramplier stage. Thus, either two pulses are obtained at the driver tube116, or one each at tubes 116 and 154. Y

It should be noted that the grid of the Fig. 3 is a schematic drawing ofthe power amplifier' circuit. The amplifier derives its plate powerdirectly from a 117 volt D. C. service line. It comprises a plurality oftriodes connected in parallel and, either in single-ended or push-pullarrangement, depending upon whether output pulses of the same oropposite polarity are desired. The single-pole double-throw switch 156and the double-pole double-throw switch 158 control the operation of theamplier. Thus, when the switches are at their solid-line position asshown in Fig. 3, the operation of the amplider is such as to provide aunit-.cycle having individual pulses of opposite polarity.

The circuit comprises a row (row 1), of triodes 160 havingindividualplate resistors 162 and grid isolating resistors 164. The triodes 160are heavily biased beyond cut-oit by connection of the isolatingresistors 164 to a source of negative voltage supply of about 120 voltsthrough a common bias resistor 166,` A diode 168 across the biasresistor 166 clamps the bias at this lixed value. Thus, no current ilowsthrough the tubes except when a pulse is received from the pulsegenerator and synchronizer circuit (Fig. 2). r[he circuit is arranged asa cathode follower, the output load being connected across the commoncathode resistor 170 connected between the cathodes of the triode 162.and ground. The parallel triodes 160 of row 1 serve to amplify thepositive output pulse of the unit-cycle. A similar circuit comprising aplurality of triodes 172 (row 2) is connected to receive the secondpulse from the pulse generator and synchronizer circuit and deliveracross a common cathode resistor 174 the second 0r negative output pulseof the unit-cycle. The cathode resistors 170 and 174 are of about 200ohms each so that there is no appreciable loading ofthe massiveelectrode device.

Though the rows 1 and 2 as illustrated comprise tive triodes each, it isto be understood that more could be aded to each row to increase theoutput power of the amplier.

When the switches 156 and 158 are at the dotted-line position as shownin Fig. 3, the operation of the amplitier is such as to provide aunit-cycle having individual pulses of positive polarity. In this caseit will readily be seen that the triodes 172 of row 2 are switched tooperate in parallel with the triodes 160 through the common cathode loadresistor 170; the low impedance output terminal being connected toground.

Operation Fig. 4 illustrates the method of stimulating a muscle inaccordance with the invention. The muscle M immersed in an electrolyte Eis clamped in position at its lower end, and its upper end ismechanically connected to a recording transducer (not shown), which canbe a piezoelectric device, for example. Actuation of the transducer bythe contractile response of the muscle to stimulation produces aproportional outputl voltage that is recorded by suitable electricalrecording apparatus. The massive plates or electrodes X and Y areconnected to the output of the electric stimulator.

lf pulses in the unit-cycle of opposite polarity are desired, theswitches in Figs. 2 and 3 are set to their full-line positions. ifpulses of the same polarity are desired, the switches will be set attheir dotted-line positions. Pulse and interval widths are controlled byadjustment of the respective potentiometers in the pulse l" phantastroncircuit comprising the pentode 32, the interval phantastron comprisingthe pentode 84, and the pulse 2 phantastron comprising the phantastron85. The amplitudes of the first and second pulses are independentlycontrolled by adjustment of the potentiometers 108 and 302. in the platecircuits of triodes 102 and 146, respectively.

In order that the invention can be practiced with the least amount ofroutine circuit design, the Afollowing list of circuit element valuesfound to be satisfactory in a practical embodiment of the invention isgiven:

POTENTIOBIETERS v ohms 92 5,000 94 5,000 96 20,000 9s 500 10s 50,000 23s20,000 240 500 244 5,000 246 5,000 282 20,000 284 500 28s 5,000 2925,000 302 50,000

RESISTORS 106 500,000 134 50,000 136 5,000 50,000 162 50 164 10,000 1661,000 170 200 174 200 176 50,000 17s 5,000 180 15,000 182 5,600 1341,000 186 5,000 18s 10,000 190 25,000 192 12,000 194 3,000 196 33,00019s 500,000 200 40,000 202 2,700 204 150,000 206 1,200 20s 15-,000 21047,000 212 8,200 214 500,000 216 60,000 21s 50,000 220 500,000 22227,000 224 27,000 226 15,000 22s 5,600 230 1,100 232' 5,000 234 10,000236l 25,000 242 12,000 24s 3,000 250. 500,000 252- 60,000 254 *50,000256 y 500,000 25s Y 270,000 260 10,000 262 27,000 264 270,000 266 50,00026s 5,000 270 15,000 272 .5,600

Ohms

276 Y 5,000 278 10,000 280` 25,0007V 286 12,000 292 D 3,000 294 Y Y Y33,000 296 `500,000 298 4 n v Y 40,000 300 500,000 304 i K Y Y Y 150,000306 2,700 308 Y, V50,000 310 A 2,700 312 150,000 314` 1,200 V316 15,000

Y CONDENSERS 100 microfarads 16 104 do 4 130 do 50 318 micromicrofarads200 320 microfarads 0.09 Y 322 do V1 324 i do 4 326 d0 2. V328 do 0.2330 do 0.5 332V Ydo 16 334 Y do 0.05 336 rnicromicrofarads 500 338microfarads 0.09 340 l do 16 342 do 0.2 344j do 0.5 345 Y do `16 346 do348 Y Y do V 0.05 350 micromicrofarads 500 352 microfarads y0.09 354 doi1 356 do Y 4 358 do 4 360 do -Y 2 368 d0 V16 VACUUM TUBES 82` "6SA76SA7 6SA7 '6SN7'GJ/z) r102 6SL7'(1/2) 6H6(1/2) Y 112 v 6s77-(1/2) 114"6'SL7(1/1`) 116V `6V6 Y 118 `6SN7'(1/2) 120 i V6SN7(1/2) 123'6SN7(1/2`) 124 '6SN7(1/2) 138 `6SN7(1/z) 140 SNTU/) 142V 6SN7(1/'2) 1446SN7(%) 146. 6SL7(1/2) 152 V6SL7(12) 154 V 6AS7 168 l6H6(1/2) 172 V6AS7362 6SN7(1/2) 364 6SN7v(1/2') 366 `6SN7(1/2) 368 6SN7.(1/2) Ohms 3706SN7,(1/2 372 6H6(Vz) 374 6H6(%) gerjvoltage impulses, for producing alirst output pulse,

means for deriving a second trigger voltage impulse coincident with anedge of said first output pulse, means actuated by said trigger voltageimpulse for producing a second output pulse, means for deriving a thirdtrigger voltage impulse coincident Vwithan edge'of said second outputpulse, means, actuated by said third trigger vol*- age impulse, forproducing a third outputpulse, a power amplifier, and means `forcombining said irst and third output pulses in saidjpower amplifier toproduce an outi put unit-cycle voltage wherein the rst pulse, an inter-Y val determinedY by the width of the second pulse, and

the third pulse appear in sequence.

2. A generator for producing rectangular pulses in a unit-cycleconsisting of first and second pulses -separated by a time intervalcomprising a source of trigger voltage impulses, means, actuated by animpulse from said source of trigger voltage impulses, for producing arst rectangular output pulse, rmeans for deriving a second triggervoltage impulse coincident with the trailing edge of said lirstrectangular output pulse, means, actuated by said second trigger voltageimpulse lfor produc-V ing a second rectangular output pulse, means forderiving a third trigger voltage impulse coincident with theV 3. Theinvention as defined in claim 2 wherein means is provided forindependently varying the duration of each of said first, second andthird rectangular pulses.

4. The invention as defined in claim 2 including switch means in saidpower Yamplifier for changing the relative polarity of said first andthird pulses so as to be of the same or opposite relative polarity,selectively.

5. A generator for producing rectangular pulses in a unit-cycleconsisting of rst and second pulses separated by a time intervalcomprising a source of trigger voltage impulses, each of which isadapted to initiate a unit-pulse cycle, a 'first phantastron circuittriggered by an impulse from said source whereby an output pulse oftrapezoidal configuration is obtained, means for shaping the trapezoidal pulse output of said rst phantastron into a rst rectangularpulse, an interval phantastron circuit, means controlled by the voltagechange comprising the trailing edge of the output pulse of said iirstphantastron for initiating a second trapezoidal output pulse from saidinterval phantastron, a third phantastron, means `controlled by thevoltage change comprising the trailing edge of the output pulse of saidinterval phantastron for initiating a third trapezoidal output pulsefrom said ythird phantastron, means for shapingthe trapezoidal pulseVoutput of said third phantastron into a second rectangular an outputunit-cycle voltage wherein the iirst rectangular pulse, the interval andthe second rectangular pulse appear in sequence.

6. The invention as dened in claim 5 including means for independentlyvarying the duration of each of said first interval and second outputpulses.

7. The invention as defined in claim 5 including switch means in saidpower ampliiier for changing the relative polarity of said iirst andsecond pulses so as to be of the same or opposite polarity, selectively.

8. A generator for producing rectangular pulses in a unit cycleconsisting of two pulses each of which is independently variable induration and amplitude, the time interval between the two pulses of eachunit being also variable, said generator comprising a source ofsynchronizing impulses each of which is adapted to initiate a unit pulsecycle, a iirst phantastron triggered by a synchronizing impulse fromsaid source and designed to yield an output pulse of trapezoidalconfiguration, means for shaping the trapezoidal pulse output of saidrst phantastroninto a iirst rectangular pulse, a first driver circuit, apower amplifier to which the said rectangular pulse is applied throughsaid rst driver circuit, means for diierentiating the trapezoidal pulseoutput of said iirst phantastron, a first blocking oscillator, means foremploying the diiferentiated iirst phantastron pulse to trigger saidiirst blocking oscillator and thereby yield a further trigger impulse, asecond phantastron, means for employing the trigger impulse from saidrst blocking oscillator to initiate conduction of said secondphantastron at a time corresponding to the instant of occurrence of thetrailing edge of said first rectangular unit pulse, a second blockingoscillator, means for employing the pulse output of said secondphantastron to trigger said second blocking oscillator and produce astill further pulse which marks the leading edge of the secondrectangular unit pulse, so that the operation of said second phantastrondetermines the time interval between the said two unit pulses, a thirdphantastron triggered by the said second blocking oscillator pulse andyielding an output pulse of trapezoidal configuration and means forshaping the trapezoidal4 pulse output of said third phantastron into arectangular pulse.

9. A pulse generator according to claim 8, further comprising means forapplyingthe rectangular pulse output from said third phantastron to saidpower ampliiier through said iirst driver circuit, whereby an output isobtained from said amplifier in which the iirst and second pulses ofeach unit cycle are of the same polarity.

l0. A pulse generator according to claim 8, further comprising a seconddriver circuit, and means for applying the rectangular pulse output fromsaid third phantastron to said power amplifier through said seconddriver circuit, whereby an output is obtained from said amplier in whichthe first and second pulses of each unit cycle are of opposite polarity.Y

No references cited.

